A continental divide acts as a naturally occurring geographical boundary, essentially a ridge, that demarcates a continent’s river systems. Imagine it as the high ground that dictates the direction water will flow. Each of these vast river systems ultimately empties into a distinct ocean basin, sea, or bay.
Continental divides are large-scale examples of what are known as drainage divides, or simply divides. These divides are boundaries that separate drainage basins or watersheds of varying sizes. Whether on a grand continental scale or a smaller local scale, drainage divides are always situated in elevated terrain, such as mountain ranges or hills.
Alt text: Map illustrating the Continental Divide of the Americas, highlighting the separation of watersheds flowing to different oceans.
Generally speaking, precipitation, whether rain or snow, that falls on one side of a continental divide will flow towards one specific basin, while precipitation on the opposite side will drain into another basin entirely. This simple principle governs the vast drainage patterns across continents.
However, there are exceptions. In some instances, water may flow towards an endorheic basin. These are inland drainage basins that do not drain out to an ocean or other large body of water, often terminating in salt lakes or salt flats. Endorheic basins are more commonly found in arid and desert regions. A significant portion of the Sahara Desert in Africa is an example of an endorheic basin. Rivers and streams flowing into Lake Chad, located on the Sahara’s edge, have no outlet to the Mediterranean Sea or the Atlantic or Indian Oceans.
Continental divides are a feature of every continent on Earth. Continents bordered by more than two major bodies of water can even have multiple continental divides. For instance, North America is considered to have between three and five divides, although a definitive number remains debated by scientists due to the lack of universal agreement on the precise boundaries between ocean basins.
Alt text: Diagram showing the multiple continental divides across North America, indicating different drainage regions and their outlets.
Certain continental divides extend across multiple continents. The most prominent example is the Continental Divide of the Americas, also known as the Great Divide. This massive divide stretches across a significant portion of both North and South America. It serves to separate waters flowing westward towards the Pacific Ocean from those flowing eastward towards the Atlantic and Arctic Oceans, as well as the Gulf of Mexico. The Great Divide’s path begins at Cape Prince of Wales in western Alaska, traverses the Rocky Mountains throughout western Canada and the contiguous United States, continues through the Sierra Madre Occidental mountains in Mexico and Central America, and finally runs along the Andes Mountains of South America. This extensive geographical feature plays a crucial role in shaping the hydrology and landscapes of the Americas.
